Transmitted signals, and particularly millimeter wave (mmWave) signals, can be blocked by obstructions such as a human hand. Blocked transmission paths can cause unreliable communication in wireless networks. Transmission path obstructions may be avoided by changing the beam used to perform the transmission at the base station. Hybrid beamforming can be used in mmWave communication to direct signals around transmission path obstructions, which can reduce signal path loss in high-frequency bands. Hybrid beamforming splits precoding and combining of signals between the baseband and RF layers of the transmitter.
In hybrid beamforming, a transmission is divided into transmission groups, with each transmit group including one transmit antenna port. Each transmit antenna port may transmit using one of several possible transmit beam ports. A user equipment (UE) may select a transmit beam port during a defined beam scanning opportunity in the network. The transmit beam ports for each transmit antenna port at the base station may be used to sequentially transmit reference signals during a beam scanning opportunity. The UE scans for signals from all transmit beam ports from the base station during a beam scanning opportunity and indicates a preferred transmit beam port.